1. Field of the Invention
The invention relates to pipe connection joints, particularly but by no means exclusively for sea-bed pipework.
2. Description of the Prior Art
There is frequently a requirement for a non-weldable but permanent pipe connection joint in both subsea and surface applications. In addition, for subsea applications in particular, it is desirable that a pipe connection joint should also possess the capability of telescoping to allow disconnection of an adjacent connector.
In the installation of a subsea template or manifold system on the sea-bed, sea-bed flowlines have to be laid from either a platform or a land installation. With a deep water application it is usual, because of the complexity of the operation, to pull a line into its final position and, after retaining it at the junction, to effect the final connection to the manifold or template pipework in a separate operation. This final connection can be effected in a number of ways, but in all cases it is usual to spread the pipe ends apart in order to interpose seals or a seal carrier and then to pull them together and pressure clamp the pipe ends.
Thus provisions have to be made to allow for spreading apart of the pipe ends when the final connection is made. For this purpose telescopic joints have in the past been proposed, and although such joints are inherently attractive they have attracted severe criticism on two main grounds. Firstly, the resilient seals which have been necessary to prevent leakage could not be guaranteed to remain effective over long periods and, secondly, the joints generally had to be restrained to prevent end pressure parting.
The present state of the art relating to subsea installations generally avoids the problems with telescopic joints by utilising either flexible pipe spools or flex loops within the manifold pipework structure which deflect appropriately to allow spreading of the pipe ends to be connected. As will be appreciated this requires large pipe bends to be incorporated to accommodate the required deflection without over-stressing of the pipe loops. The desired result can be achieved with outboard sea-bed flowline deflection, and although this reduces the size of the template and manifold structure the successful deflecting back of the flowline to make the final connection is not predictable, and indeed the success of this operation cannot be guaranteed.